Studies on ≥1 hectare permanent plots in the Amazon indicate accelerating forest dynamics and increasing biomass in old-growth forests over the last 30 years. Similar results have been found in forest plots in Africa and, to a lesser degree, in Asia, providing evidence that increasing carbon storage in old-growth forests might be a pan-tropical phenomenon.
Several explanations have been put forward to explain these observed changes, including the effects of increased atmospheric CO2 concentration due to the burning of fossil fuels, the effects of changing climate, recovery from past disturbances and the effects of increased nutrient depositions.
The stable isotope record in the cellulose of tree rings could provide more insight in the factors causing long-term changes in tropical forests. One of the main objectives of my PhD research is to reconstruct the (local) climatic conditions for the last 150-200 years in TroFoClim fieldwork areas. A special focus will be on the frequency of droughts. Trying to reconstruct climatic conditions is challenging and I am therefore using three different tree ring parameters: ring width and carbon and oxygen isotopes. All are, in different ways and degrees, influenced by climate. The second main topic of my PhD research is to find indications for the so called ‘CO2 fertilization effect’ by using carbon isotopes as a proxy for internal [CO2] in the leaves (ci). Very simplistic; if increasing atmospheric CO2 concentration allows plants to absorbed CO2 with less water loss, we expect them to be able to maintain higher ci levels. If water is a limiting factor (during some parts of the day or of the year), a lower water loss might allow plants to extent their growth into the dry season or during the drier parts of the day, hence explaining increased growth rates.
My PhD research is part of a pan-tropical study on the long-term changes of growth and dynamics in tropical forests and the potential factors causing them (the TROFOCLIM project). I am working at the Bolivian fieldwork site; the 100.000 ha FSC forest concession of La Chonta. My final data set will, however, also include trees from Thailand and Cameroon (see PhD projects of Mart Vlam and Peter Groenendijk).
- Robbert Haasnoot & Jeroen Buijks. The effects of different logging strategies on growth and timber yields of Hura crepitans
- Quirine Hakkaart & Annemarijn Nijmeijer. Reconstructing climate (drought) in Eastern Bolivia using tree rings width and stable isotopes
Understanding causes of tree growth response to gap formation: D13C-values in tree rings reveal a predominant effect of lightTrees-Structure and Function 28 (2014)2. - ISSN 0931-1890 - p. 439 - 448.
Environmental and physiological drivers of tree growth : a pan-tropical study of stable isotopes in tree ringsWageningen University. Promotor(en): Pieter Zuidema; Frans Bongers; Niels Anten. - Wageningen : Wageningen University - ISBN 9789461739544 - p.
Herbivory and habitat association of tree seedlings in lowland evergreen rainforest on white-sand and terra-firme in the upper Rio NegroPlant Ecology & Diversity 7 (2014)1-2. - ISSN 1755-0874 - p. 255 - 265.
No growth stimulation of tropical trees by 150 years of CO2 fertilization but water-use efficiency increasedNature Geoscience 8 (2015). - ISSN 1752-0894 - p. 24 - 28.
Tropical forests and global change: filling knowledge gapsTrends in Plant Science 18 (2013)8. - ISSN 1360-1385 - p. 413 - 419.
WP4: Existing strategies to exchange nutrient between firms: s.n. - p.
Manejo de bosques tropicales: bases científicas para la conservación, restauración y aprovechamiento de ecosistemas en paisajes rurales.Investigación Ambiental. Ciencia y Politica Publica 4 (2012)2. - ISSN 2007-4492 - p. 111 - 129.
Tree communities of white-sand and terra-firme forests of the upper Rio NegroActa Amazonica 41 (2011)4. - ISSN 0044-5967 - p. 521 - 544.
Terburg, G. (2012). Long-term growth and internal carbon dioxide trends in Hura crepitans show little change in growth, climatic and environmental drivers in a forest in Bolivia.